Cardiac arrest is a life-threatening medical condition that may be treated with external defibrillation. External defibrillation includes applying electrodes to the patient's chest and delivering an electric shock to the patient to depolarize the patient's heart and restore normal sinus rhythm. The chances that a patient's heart can be successfully defibrillated increase significantly if a defibrillation pulse is applied quickly.
Until recently, individuals such as paramedics, emergency medical technicians, police officers and others trained in defibrillation techniques used defibrillators, but the general public did not. In some cases, the patient's need is urgent and the patient cannot wait for trained personnel to arrive. In recognition of the need for prompt treatment, automated external defibrillators (AED's) are becoming more commonplace, and are available in venues such as airports, health clubs and auditoriums.
When an AED is used to treat a patient, much of the treatment is performed by the AED rather than the person who operates the AED. In general, the AED automatically measures the patient's cardiac signals, assesses whether a shock is indicated and charges a storage element in preparation for giving the shock. When a shock is indicated, the AED may cue the operator to administer the shock, or the AED may administer the shock automatically. In addition, many AED's include visual displays, voice instructions and other audible messages that tell the operator about the status of the defibrillator.
Placement of defibrillation electrodes on the patient's chest, however, cannot be performed by the AED. In many AED's, the electrodes are packaged in a sealed pouch. The operator must open the pouch, retrieve the electrodes and place the electrodes in the correct positions on the patient's chest. In many cases, a minimally trained operator, properly instructed, can place the electrodes on the patient's chest in the correct positions. Without instruction, the operator could put one or both electrodes in an incorrect anatomical placement.